NASA’s Nancy Grace Roman Space Telescope will study muffled stellar currents that extend far beyond the apparent edges of many galaxies. Missions like the Hubble and James Webb space telescopes would have to collect hundreds of small images to see these structures around nearby galaxies in full. Roman will do it in one snapshot. Astronomers will use these observations to explore the growth of galaxies and the nature of dark matter.
Stellar currents resemble ethereal locks of hair that extend outward from certain galaxies and drift peacefully through space as part of the halo – a spherical region that surrounds a galaxy. But these stellar flights are signs of an ancient cosmic-scale drama that serves as a fossil record of a galaxy’s past. Studying them turns astronomers into galactic archaeologists.
Particularly elusive stellar currents that formed when the Milky Way sucked stars from spherical star clusters have been discovered before, but they have never been found in other galaxies. They are weaker because they contain fewer stars, making them much harder to spot in other, more distant galaxies.
Roman was able to discover them in several of our neighboring galaxies for the very first time. The mission’s wide, sharp and deep view should even reveal individual stars in these enormous dark structures. In a previous study, Pearson led the development of an algorithm to systematically search for stellar fluxes from globular clusters in nearby galaxies.
Starkenburg’s new study adds to the picture by predicting that Roman should be able to detect dozens of currents in other galaxies from dwarf galaxies, providing an unprecedented insight into the growth of galaxies.
“It’s exciting to learn more about our Milky Way, but if we really want to understand galaxy formation and dark matter, we need a bigger sample,” Starkenburg said. “Studying stellar fluxes in other galaxies with Roman will help us get the big picture.”
The Nancy Grace Roman Space Telescope is operated by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation from NASA’s Jet Propulsion Laboratory and Caltech / IPAC in Southern California, the Space Telescope Science Institute in Baltimore and a scientific team composed of scientists from various research institutions. The major industrial partners are Ball Aerospace and Technologies Corporation of Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
“Halos are mostly stars that have been torn from other galaxies,” said Tjitske Starkenburg, a postdoctoral fellow at Northwestern University in Evanston, Illinois, who has studied the potential of the novel in this area. “The wide and deep images of the novel will be sharp enough for us to dissolve individual stars in the halos of other galaxies, making it possible for the first time to study stellar fluxes in a large number of galaxies.”
The team, led by Starkenburg, will share their findings at the 240th meeting of the American Astronomical Society in Pasadena, California, today.
Galactic cannibalism, stolen stars
The simulations support the theory that galaxies grow in part by engulfing smaller groups of stars. A dwarf galaxy trapped in the orbit of a larger galaxy is distorted by gravity. Its stars rain and trace arcs and loops around the larger galaxy until they finally become its newest members.
“When individual stars escape the dwarf galaxy and fall into the more massive, they form long, thin streams that remain intact for billions of years,” said Sarah Pearson, Hubble Postdoctoral Fellow at the university. from New York to New York and the lead author for a separate study of the mission’s expected observations in this area. “Thus the stars’ flux contains secrets from the past and can shed light on billions of years of evolution.”
Astronomers have captured this cannibalistic process on fresh deed by using telescopes like ESA’s (European Space Agency) Gaia satellite, which is fine-tuned to measure the positions and movements of the stars in our Milky Way galaxy. The novel will expand these observations by making similar measurements of stars both in the Milky Way and in other galaxies.
The Milky Way is home to at least 70 stellar currents, meaning it has probably eaten at least 70 dwarf galaxies or spherical star clusters – groups of hundreds of thousands of gravitational stars. The novel’s Milky Way images could allow astronomers to collect snapshots in time to show the stars’ motion. This will help us understand what dark matter is made of – invisible matter that we can only detect by its gravitational effects on visible objects.
One theory suggests that dark matter is “cold” or consists of heavy, slow-moving particles. If so, it should clump together in galactic halos and disrupt stellar currents in ways that Roman could see. By detecting or eliminating these distortions, Roman was able to narrow the candidates to dark matter composition.
Astronomers are also eager to study stellar currents in several of the Milky Way’s neighboring galaxies. They are not well studied in other galaxies because they are so weak and so far away. They are also so large that they can wrap around an entire galaxy. It takes a unique panoramic view like Romans to take pictures that are both large and detailed enough to see.